I will say this for Rick Santorum: He's one of the more well-spoken bigots I've heard in a while. His defense of his absolutist position on gay marriage, delivered in front of a largely hostile crowd of college Republicans in Concord, N.H., was concise, logical and delivered with the rhetorical flourish of a seasoned attorney. None of it hadn't been expressed by same-sex marriage opponents before, but Santorum's gift is to make his morally and legally untenable position sound reasonable.

Boiled to its essence, his argument has three parts: First, the burden of demonstrating that same-sex marriage should be legalized falls on its supporters rather than its opponents, because the former group is the one that wants to change the law. Fair enough. Here's the reason, Rick: Because discriminating against a class of people by failing to grant them the same rights enjoyed by everyone else is unfair and unconstitutional.

The second part of Santorum's argument is that many of the legal benefits of marriage, such as the right to visit a hospitalized spouse, can be obtained via legal contract, so why should gays insist on marriage rights? This is monstrously disingenuous, as Santorum the lawyer well knows, but it seemed to confuse the crowd, so apparently there weren't any law students among them. Santorum is correct that property and inheritance rights can be transferred to another via contract -- gay partners can leave their houses to each other in their wills, for example. But, as Oakland attorney and author Fred Hertz explains, public benefits -- tax advantages, health insurance and so on -- can't be transferred via contract, except in states that recognize domestic partnership agreements (and most states, including Santorum's native Pennsylvania, don't). Even in the domestic partnership states, no federal tax, Social Security or other benefits apply to such partners because of the 1996 Defense of Marriage Act.

Finally, there is Santorum's third argument, which by now is pretty familiar to anyone following the same-sex marriage debate: If you allow same-sex couples to marry, why not allow polygamy? This one's tougher to refute because it gets to a truism that gay-marriage proponents don't like to discuss -- there is a social-values component to marriage. Religious conservatives see no distinction between same-sex marriage and incest or polygamy, because to them, all of these things represent sexual sins. Yet there are obvious differences.

Setting aside the ick factor of incestuous marriage, sexual liaisons between family members can lead to offspring with terrible genetic abnormalities. Polygamy is slightly less objectionable on its face, but in practice it causes enormous social problems -- polygamous societies inevitably create a surplus population of young, restive males who end up on the streets or fuel upheaval because they can't find wives, most of whom have been snapped up by powerful older men. Underage women are frequently forced into marriages with much older men, and there is an innate power imbalance built into any relationship between one man (or one woman) and multiple partners of the opposite sex.

But more important than any of these distinctions is the fact that the entire comparison is irrelevant. There is no mainstream political movement in this country to legalize polygamy or incestuous marriage; when and if there is, we can debate whether it's appropriate. By dragging these things into the debate over same-sex marriage, Santorum and his ilk are simply playing reductio-ad-absurdem rhetorical games. This technique can be used to discredit nearly any position on anything: If we allow same-sex marriage, what's next, people marrying dogs? If we allow people to drink alcohol, why not let them snort cocaine? If we guarantee the right to bear arms, why not guarantee the right to build thermonuclear devices in one's garage?

The answer: Because it's ridiculous. Let's stick to the matter at hand -- whether consenting adults of the same sex should be allowed to marry. It's OK to agree with Santorum that they shouldn't, but let's not drag the cast of "Big Love" into the discussion.